The present inventions relate to fiber optic cables and, more particularly, to interconnect cables containing optical fiber ribbons and breakout cables having provisions for breaking one or more interconnects out of the cable so that optical fibers of the cable can be connected to various devices.
Fiber optic cables of the type described above have been made with various constructions. One such cable includes an extruded plastic core having slots formed in its periphery, and a plurality of optical fiber ribbons disposed in each of the slots, a buffer tube being extruded over the ribbons, and a protective outer jacket being extruded thereover. The core can include a strength member embedded in its center. The slots typically extend helically such that the ribbons are stranded about the core. A drawback of this cable is that once a ribbon is broken out from the buffer tube it is relatively unprotected. Consequently, this cable is not particularly suitable for applications in which a broken-out ribbon may be subjected to considerable forces during routing of the ribbon or in operation, since the ribbon may be damaged or broken.
It would be desirable to provide a fiber optic breakout cable that facilitates protecting the ribbons broken out from the cable. It is also desirable to minimize the cross-sectional size of a fiber optic ribbon breakout cable. The cable size is reduced in general by increasing the packing density of fibers in the cable, such that a given number of fibers can be contained in a smaller cable.
The present invention provides interconnect cables and fiber optic ribbon breakout cables facilitating a high packing density and having features for protecting ribbons broken out from the cable. In one aspect of the invention, a fiber optic interconnect cable has a robust construction for reliable performance. In accordance with another aspect of the invention, the fiber optic cable comprises a core formed as a generally rod-shaped structure and having a plurality of slots formed in an outer surface of the core and extending generally lengthwise therealong, an outer jacket of tubular form surrounding the core, and at least one interconnect ribbon cable disposed in each of the slots of the core. Each interconnect ribbon cable comprises a tubular jacket defining an interior passageway and at least one optical ribbon disposed in the interior passageway of the tubular jacket. The fiber optic breakout cable in accordance with the invention can also include additional elements, such as one or more strength members, an armor layer, ripcords, and/or other features.
The core can be formed of a solid or a foamed polymer material. Various numbers of slots can be formed in the core, and the slots can all be of the same radial depth or can have different depths such that the deeper slots contain a greater number of optical fibers than the shallower slots. For example, the core can have shallow slots and deep slots arranged in an alternating fashion about the core""s circumference, with the shallow slots each containing one interconnect ribbon cable and the deep slots each containing two interconnect ribbon cables.
Each interconnect ribbon cable can contain a plurality of ribbons arranged in a stack, if desired. Each ribbon can have from two to 36 fibers. A slip layer of low-friction tape or yam can be provided between adjacent ribbons of a stack to facilitate relative sliding between the ribbons for enhancing optical performance. The interconnect ribbon cables can also include one or more strength members. Thus, the tubular jacket of a interconnect ribbon cable broken out from the cable provides protection to the ribbon(s) contained within the interconnect cable. Additionally, where the interconnect cable includes strength members, the interconnect cable is capable of withstanding tensile forces such as may be exerted in pulling the interconnect cable along a path during installation.
In accordance with another aspect of the invention, a fiber optic cable comprises a tubular outer jacket defining a central interior passageway therein, and a group of interconnect ribbon cables disposed in the interior passageway of the outer jacket, each interconnect ribbon cable comprising at least one optical ribbon and a tubular jacket surrounding the at least one optical ribbon. The plurality of interconnect ribbon cables includes at least one conjoined pair of interconnect ribbon cables having the tubular jackets thereof attached together in a manner allowing one of the interconnect ribbon cables to be separated from the other by breaking a connection between the tubular jackets of the interconnect ribbon cables. Preferably, the conjoined pair of interconnect cables are made by simultaneously extruding both tubular jackets of the two cables from a common die having a middle portion defining a web connecting the two jackets. The invention is not limited to having only two conjoined interconnect cables; three or more interconnect cables can be conjoined, if desired.
In one embodiment, there are a plurality of conjoined pairs of interconnect ribbon cables stacked together. A single interconnect ribbon cable can be arranged at each end of the stack to further increase the packing density of the cable.
The cable in accordance with the second aspect can also include a buffer tube surrounding the interconnect ribbon cables, with the outer jacket of the cable surrounding the buffer tube. If desired, strength yarns or the like can be disposed between the buffer tube and the outerjacket for increasing the strength of the cable.